Void reducing asphalt membrane composition, method and apparatus for asphalt paving applications

ABSTRACT

A roadway structure that includes: a substrate; a hot mix application portion positioned over the substrate, wherein said hot mix application portion comprises first and second adjacent paving passes defining a longitudinal joint, and wherein the first and second adjacent paving passes contain air voids along the longitudinal joint; and a spray-applied band of void reducing joint composition positioned between the substrate and the hot mix application portion, wherein the band is below the longitudinal joint, and wherein at least at portion of the void reducing joint composition fills at least some of the air voids.

RELATED APPLICATIONS

The present application is a continuation of U.S. Non-Provisionalapplication Ser. No. 16/276,214, filed Feb. 14, 2019, which is acontinuation of U.S. Non-Provisional application Ser. No. 16/103,466,filed Aug. 14, 2018, which is continuation of U.S. Non-Provisionalpatent application Ser. No. 15/646,912, filed Jul. 11, 2017, which is acontinuation of U.S. Non-Provisional application Ser. No. 15/401,995,filed Jan. 9, 2017, which is a continuation of U.S. Non-Provisionalpatent application Ser. No. 15/064,819, filed Mar. 9, 2016 which isbased upon U.S. Provisional Application Ser. No. 62/130,293, filed Mar.9, 2015 and 62/302,335 filed Mar. 2, 2016 to each non-provisional andprovisional applications priority is claimed under 35 U.S.C. § 120 andof each of which the entire disclosures are hereby expresslyincorporated by reference.

TECHNICAL FIELD

The present invention relates to installation and preventive maintenanceof asphalt paved surfaces. More particularly the present inventionrelates to void reducing asphalt membrane compositions and methods forbonding and reducing voids in longitudinal asphalt pavement constructionjoints in a variety of paved surface construction joint applications andequipment/apparatus for applying a void reducing asphalt membranebeneath or on the vertical face of longitudinal asphalt pavementconstruction joints.

BACKGROUND ART

The cracking of longitudinal asphalt pavement construction joints is acommon pavement distress associated with asphalt pavements. When anasphalt pavement is constructed the width of the pavement is limited bythe width of the screed or screed extensions. This width can vary from 8feet to a maximum of about 35 feet in special cases. Pavement widthsthat are greater than the maximum screed width require the formation ofa longitudinal asphalt pavement construction joint where the hot mixasphalt is paved against the edge of previously laid portion of thepavement. In many situations, the reconstruction of roadways may notallow for full closure to traffic. In such situations which are typical,paving width is limited to one lane (normally 12 feet or 3.6 meterswide) while vehicular traffic is redirected onto an adjacent pavement.This limitation forces the next lane to be placed against the firstpavement forming a longitudinal asphalt pavement construction jointbetween the lanes.

There are a number of deficiencies that are associated with longitudinalasphalt pavement construction joints. For example, the unconfined edgesof a first pass of the pavement cannot be compacted to the same degreethat the center of the first pass is compacted. Compaction increasesdensity and reduces air voids which are critical to the performance ofasphalt pavements. After the first pass is completed an adjacent passplaces a hot paving mixture against the now cold first paving pass,creating a longitudinal asphalt pavement construction joint between thetwo paving passes or lanes.

As a result, the area along the longitudinal asphalt pavementconstruction joint is higher in air voids, creating permeability to airand water causing the joint to be subject to oxidization and aging morerapidly than the rest of the pavement. The area along the longitudinalasphalt pavement construction joint can be a foot in width where the airvoids are higher than the area in the middle of the paving lane. Inareas where freeze/thaw occurs, water can intrude into the permeablejoint and adjacent area and freeze. As these events occur, the jointbecomes significantly weaker than the rest of the pavement, resulting ina greater tendency for the joint to crack from heating and cooling(expansion and contraction) of the adjacent pavement.

Once cracks form along longitudinal asphalt pavement construction jointsthey allow more water and air to penetrate into the underlying layers ofthe pavement, causing more damage to the joint and underlying pavementlayers. This accelerates the development of fatigue cracks radiatingoutward from longitudinal cracks which often widens the longitudinalcracks and accelerates the overall damage to the pavement structure.

The initiation of longitudinal asphalt pavement construction jointcracks is caused by the shrinkage of asphalt surface due to pavementheating and cooling cycles from day to night and summer to winter. Thecracking occurs at the longitudinal asphalt pavement construction jointbecause the density of the joint is lower than the rest of the pavementcausing a weak bond to be formed. The joint has the lowest tensilestrength in the pavement and fails first when the pavement contracts asit cools. A second factor in longitudinal asphalt pavement constructionjoint cracking is oxidative hardening of the asphalt due to high airvoids in the mixture in the joint area which makes that materialparticularly susceptible to cracking and subsequent raveling. Theasphalt mixture adjacent to the longitudinal asphalt pavementconstruction joint cracking is exposed to air and water intrusion whichcan lead to poor adhesion between the asphalt and aggregate, whichfurther causes more rapid deterioration (raveling). During early stages,these cracks are usually repaired by sealing. After raveling begins todevelop, the repair is more extensive, since the materials adjacent tothe crack must be removed and replaced. These maintenance activities arelabor intensive and create safety concerns for the maintenance crewssince they are usually performed when the pavement is under trafficconditions. This also causes traffic delays for the motoring public.

Longitudinal asphalt pavement construction joint cracking and subsequentraveling degrade pavement serviceability, shorten pavement life andincrease life cycle cost. Therefore the reduction or elimination oflongitudinal asphalt pavement construction joint cracking results inreduced life cycle costs and increased pavement life.

There are two primary approaches that have been traditionally used todelay longitudinal asphalt pavement construction joint crackingproblems. One approach is to make the joint stronger than the adjoiningmaterial so that the pavement will not fail at the joint undertemperature expansion/contraction. Joint compaction techniques areattempts to prevent cracking in this manner. The second approach tocrack prevention is to put very elastic pliable material into the jointduring the pavement construction. When this method is used, as thepavement contracts, the joint material simply flows to release thestress.

Mechanical devices have been developed which are intended to compact theunconfined edge of pavement or cut the high air void edge from thepavement. In practice, this approach has not solved the problem ofcreating a strong joint which lasts as long as the pavement.

Other approaches involve providing an elastic pliable material in theform of a tape at the pavement joint. This tape is placed against a coldlongitudinal asphalt pavement construction joint of the pavement. Beforeuse, the joint is cleaned so as to be free of dirt and unbondedmaterial. The edge of the joint tape is then applied to be flush withthe surface of the pavement. Next, the non-stick release paper isremoved and the placement of the adjacent pavement section is completed.Once the hot mix asphalt is placed against the tape, the tape melts,binding the joint together.

Comparison between pavements installed with joint tape and thoseinstalled without a joint tape indicate that the joint tape provides ajoint that lasts longer before cracking. The air void content at theimmediate area of the joint are reduced and therefore, the joints areless permeable to water. While the joint tape can help address the bondbetween the adjacent pavement layer and reduce the air voids at theimmediate joint face, it fails to address the higher air voids up to afoot away from the joint. Another deficiency of joint tape is the highlabor to physically prepare/clean the area and install the material

Studies conducted on highways on a life cycle basis find that pavementsin the northern part of the United States develop longitudinal asphaltpavement construction joint cracking within 2 to 3 years after placementof hot mix asphalt. The current treatment strategy is to crack fill thejoint with a standard polymerized asphalt or crumb rubber asphalt. Theproblem is that this topical treatment does not treat the damage causedby water which reaches further into the pavement prior to treatment.Highway departments find that current treatment protocols only last 3 to4 years after which the crack fill is repeated. Ordinarily pavementscurrently last 13 years on average. This relatively short 13 year lifeoften is due to damage near the longitudinal asphalt pavementconstruction joint.

The present invention provides void reducing asphalt membranecompositions and placement that overcome many of the disadvantagesassociated with known joint materials and installation techniques.

DISCLOSURE OF THE INVENTION

According to various features, characteristics and embodiments of thepresent invention which will become apparent as the description thereofproceeds, the present invention provides for void reducing asphaltmembrane compositions that can be placed in a band on an existingpavement surface that defines the first substrate in the area where thenew longitudinal joint(s) will be constructed. The band of void reducingasphalt membrane is wide enough to be beneath the area of the newpavement lift that is typically low in density, high in air void volume.The band of void reducing asphalt membrane is in sufficient thickness toallow migration into the new asphalt mixture lift overlay and reduce theair void volume and ability for water to infiltrate and damage the newasphalt mixture overlay and underlying structure. The band of voidreducing asphalt membrane can be driven over by the constructionequipment or the traveling public and not be displaced or picked up ontires/tracks and removed from its intended location. The band of voidreducing asphalt membrane will not flow laterally from its intendedplacement location. The void reducing asphalt membrane will adhere tothe existing pavement surface, whether it is asphalt concrete, Portlandcement concrete, milled asphalt concrete or Portland cement concrete,brick or chip seal surface, etc. The void reducing asphalt membranecomposition generally comprises a mixture of asphaltic binder,elastomeric polymers, thickener and additive to reduce tackiness.

The present invention provides a method of forming a pavementconstruction joint, comprising:

dispensing a band of a void reducing joint composition on a substrateusing at least one spray application vehicle, wherein the band comprisesa width of about 4 to about 24 inches;

permitting the application of a paving pass over the band of jointcomposition, wherein the paving pass is positioned against an edge of apreviously laid portion of pavement to form a pavement constructionjoint having a volume of air voids; and

allowing at least a portion of the joint composition to migrate upwardto reduce the volume of air voids.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is directed to a new preventative maintenanceproduct and process for pavement construction involving hot mix asphaltand particularly to the construction of joints between adjacentpavements and non-asphaltic surfaces such as concrete.

The present invention provides void reducing asphalt membranecompositions which, when used in pavement applications, are placed belowthe new lift of asphalt mixture pavement and/or against a cold joint onthe vertical face of a newly created lift of asphalt mixture pavementbefore an adjacent hot mix is put down against or over the cold joint toform a good bond between the cold joint and hot mix and reduce air voidsand water permeability and create better crack resistance in the area ofthe joint. The void reducing asphalt membrane compositions of thepresent invention have been formulated so as to be resistant to lateralflow prior to paving over with hot mix asphalt in order to remain in thejoint area in sufficient quantity to fill voids. At the same time thevoid reducing asphalt membrane composition is formulated so that it canbe applied in a sufficient thickness to allow it to migrate upward intoa freshly placed asphalt overlay during a paving process to reduce airvoids and reduce water permeability. In multi-pass pavement applicationsthe void reducing asphalt membrane composition can be provided betweenadjacent passes of asphalt, including on the vertical face or edge of afirst or previous pass. Further a conventional tack coating can beprovided under a first or previous pass alone or together with a band ofthe void reducing asphalt membrane composition.

The void reducing asphalt membrane composition is sufficientlynon-tracking or loses its tackiness quickly so as to allow forconstruction traffic to drive over the applied composition duringplacement of an asphalt overlay or an adjacent pass and avoid workstoppage during a paving operation. Generally after application the voidreducing asphalt membrane composition may be driven across byconstruction traffic or other vehicular traffic within 30 minutes ofplacement or as within as little as 15 minutes or less of placement.This ability to be non-tracking or quickly lose any tackiness solvesconstructability issues that plague other approaches to pavement jointconstruction.

The composition includes polymerized asphalt which allows a joint formedtherefrom to expand and contract elastically, thus dissipating expansionand contraction forces. The highly compliant material behaves like anexpansion joint in pavement applications which prevents stresses frombuilding up at the joint which would otherwise tend to cause cracks toform and subsequent pavement failure.

The void reducing asphalt membrane composition of the present inventiongenerally comprises a mixture of an asphalt binder, elastomericpolymers, a thickener and a wax modifier. Other embodiments comprise anasphalt binder, elastomeric polymers, a thickener, a wax modifier andfumed silica and/or fumed alumina. Further embodiments include anasphalt binder, elastomeric polymers, a thickener, a wax modifier and asaponified fatty acid and a resin acid gelling compound. Still furtherembodiments comprise an asphalt binder, elastomeric polymers, athickener, a wax modifier fumed silica and/or fumed alumina and asaponified fatty acid and a resin acid gelling compound.

The asphalt binder is the main component of the composition and providesthe material strength or foundation to fill voids in the area of thelongitudinal asphalt pavement construction joint. The asphalt binder cancomprise 85 to 97 wt. % of the composition and more preferably 90 to 93wt. % of the composition. Suitable asphalt binders include paving gradeasphalts including; performance graded, viscosity graded or/orpenetration graded.

The composition includes an elastomeric polymer component that allowsthe area in and around the longitudinal asphalt pavement constructionjoint formed therefrom to expand and contract elastically. The polymercomponent creates a polymer modified asphalt binder in combination withthe asphalt binder component. Suitable examples of this polymercomponent include Styrene-Butadene-Styrene (SBS), Styrene-ButadeneRubber (SBR), Ethylene-Styrene-Interpolymers (ESI), Evaloy (an ethyleneterpolymer available from Dupont), and other elastomeric polymers thatare used in polymer modified asphalt compositions. This polymercomponent can comprise 1 to 6 wt. % of the composition and morepreferably 2 to 5 wt. % of the composition.

The wax modifier reduces the viscosity of the composition at the pavingtemperature so that during a paving process the composition can migrateupward into a freshly placed asphalt overlay to reduce air voids andreduce water permeability. Furthermore, at pavement surface temperature,the wax modifier provides stiffness to the void reducing asphaltmembrane which reduces issues with tracking. Suitable wax modifiersinclude, but are not limited to, waxes of vegetable (e.g. carnuba wax),animal (e.g. beeswax) mineral (e.g. Montan™ wax from coal, FischerTropsch wax from coal) or petroleum (e.g. paraffin wax, polyethylenewax, Fischer-Tropsch wax from gas) origin including oxidised waxes;amide waxes (e.g. ethylene bis stearamide, stearyl amide,stearylstearamide); fatty acids and soaps of waxy nature (e.g. aluminumstearate, calcium stearate, fatty acids). The wax modifier also improvescohesion properties of the composition. The wax modifier can comprise 1to 5 wt. % of the composition and more preferably 2 to 4 wt. % of thecomposition.

The fumed silica and/or fumed alumina function as fillers and impartresistance to flow immediately after application and give a non-tackycharacter to the composition that prevents pick-up by construction andnon-construction equipment before paving is complete.

The fumed silica and fumed alumina can be used alone or together in anydesired proportion. The total amount of fumed silica and/or fumedalumina can comprise 1 to 10 wt. % of the composition and morepreferably 3 to 6 wt. % of the composition.

The saponified fatty acid and resin acid gelling compound functions tocontrol the rate at which the composition sets or cures. Suitablesaponified fatty and resin acid gelling compounds include but are notlimited to crude tall or distilled tall oil. The total amount ofsaponified fatty acid and resin acid gelling compound can comprise 0 to3 wt. % of the composition and more preferably 1 to 2 wt. % of thecomposition.

A typical formulation of the void reducing asphalt membrane compositionis made by adding the polymer component to the heated asphalt binderwhile shearing the mixture. After or before the polymer component andasphalt binder are thoroughly mixed the wax modifier can be added whileshearing the mixture followed by the addition of the fumed silica and/orfumed alumina are and saponified fatty acid and resin acid gellingcompound. The mixed void reducing asphalt membrane should be storedunder conditions of agitation and heating until application.

During the course of the present invention the inventors discovered thatwhen the final polymer composition included fumed silica and/or fumedalumina the resulting polymer composition demonstrated improved heatstability. Furthermore the polymer properties imparted to thecomposition remained more consistent over time while at an elevatedtemperature as compared to a similar composition that did not includefumed silica and/or fumed alumina.

In a typical application the void reducing asphalt membrane compositionof the present invention is placed in a band from 4 to 24 inches wide onthe surface to be paved (also referred to as a cold joint portion) inthe area where a longitudinal construction joint of an asphalt overlayor pass will develop. Subsequently the asphalt overlay or pass is laiddown. In the case of multi-pass pavement installations before anadjacent paving pass is placed, a band of the void reducing asphaltmembrane composition having a width of 4 to 24 inches is applied overand against the vertical face portion of a previously laid pavement passin the area where the longitudinal joint will occur under the adjacentpaving pass. The thickness of applied band of void reducing asphaltmembrane compound in any situation can be 1/16 to ⅜ of an inch dependingon the overlay type and thickness. These widths and thickness ranges areexemplary of typical applications; however, it is to be understood thatother widths and thicknesses and combinations thereof could be used. Thethickness of the applied band can be adjusted to allow migration of avolume of the void reducing asphalt membrane composition into theasphalt overlay and reduce the air void volume and ability for water toinfiltrate and damage the overlay and underlying structure. The band ofvoid reducing asphalt membrane composition can be applied to anyexisting surface to be paved including asphalt concrete, Portland cementconcrete, milled asphalt concrete or milled Portland cement concrete,brick or a chip seal surface as well as metal structures.

For paving of adjacent lanes the void reducing asphalt membranecomposition can be applied to the vertical face of the first paving passas well as on an area where the second application of the product asdescribed above will be placed.

The air void volume in the finished asphalt overlay in the area of thelongitudinal asphalt pavement construction joint above the void reducingasphalt membrane composition can be reduced to about 7% or lower due tothe migration of the product into the finished asphalt overlay. Inpreferred embodiments the air void volume of the finished asphaltoverlay will be reduced to 4% in the finished asphalt overlay in thearea above the void reducing asphalt membrane composition.

In the area of the longitudinal asphalt pavement construction joint theasphalt overlay mixture will be of low permeability to waterinfiltration as a result of the void reducing asphalt membranecomposition migration into the asphalt overlay. The area of thelongitudinal asphalt pavement construction joint over the void reducingasphalt membrane composition will be resistant to crack initiation andpropagation.

The void reducing asphalt membrane composition can be applied usingvarious coating methods such as coating, rolling, spraying, etc.According to one embodiment of the present invention the void reducingasphalt membrane composition can be applied using a strike off box thatmay be mounted on mobile equipment that can be pulled or pushed eithermanually or mechanically driven. Strike off boxes that are designed foruse in narrow width paving projects are exemplified by U.S. Pat. No.8,506,204 to Reames et al. incorporated herein by reference.Alternatively conventional paving equipment downsized to apply the voidreducing asphalt membrane composition in desired widths can be used.

In other embodiments a spraying system can be used which can be mountedon mobile equipment that can be pulled or pushed either manually ormechanically driven. Otherwise the spraying can be achieved using ahandheld spraying device such as a wand.

Although the present invention has been described with reference toparticular means, materials and embodiments, from the foregoingdescription, one skilled in the art can easily ascertain the essentialcharacteristics of the present invention and various changes andmodifications can be made to adapt the various uses and characteristicswithout departing from the spirit and scope of the present invention asdescribed above and encompassed by the attached claims.

What is claimed is:
 1. A roadway structure comprising: a substrate; ahot mix application portion positioned over the substrate, wherein saidhot mix application portion comprises first and second adjacent pavingpasses defining a longitudinal joint, and wherein the first and secondadjacent paving passes contain air voids along the longitudinal joint;and a spray-applied band of void reducing joint composition positionedbetween the substrate and the hot mix application portion, wherein theband is below the longitudinal joint, and wherein at least at portion ofthe void reducing joint composition fills at least some of the airvoids.
 2. The structure of claim 1, wherein the substrate comprises apre-existing pavement roadway.
 3. The structure of claim 1, wherein thevoid reducing joint composition comprises at least one asphaltic binder,at least one elastomeric polymer, at least one thickener, and at leastone additive to reduce tackiness.
 4. The structure of claim 1, whereinthe substrate comprises at least one of an asphalt concrete, a cementconcrete, a milled asphalt concrete, a brick surface, or a chip sealsurface.
 5. The structure of claim 1, wherein the substrate comprises amilled asphalt concrete.
 6. The structure of claim 1, wherein the bandof void reducing joint composition comprises a width of about 4 to about24 inches.
 7. The structure of claim 1, wherein the void reducing jointcomposition consists essentially of at least one asphaltic binder, atleast one elastomeric polymer, at least one thickener, and at least oneadditive to reduce tackiness.
 8. The structure of claim 7, wherein theat least one elastomeric polymer comprises a styrene-butadiene-styrenepolymer.
 9. The structure of claim 7, wherein the joint compositioncomprises about 85 to about 97 wt. % of the least one asphalt binder.10. The structure of claim 1, prepared by a process that includesdispensing the band of void reducing joint composition on the substrateusing at least one spray application vehicle.
 11. The structure of claim10, wherein the band of void reducing joint composition comprises awidth of about 4 to about 24 inches.
 12. The structure of claim 11,wherein the band of void reducing joint composition is non-tracking.